1. Field of the Invention
The present invention relates to a fuel filter for removing sulfur-containing compounds from liquid fuels, and to methods of using same. More particularly, the present invention relates to an in-line fuel filter for removing thiophenes and similar compounds from liquid fuels at a point of use thereof, and to methods of filtering fuels using the described filter.
2. Description of the Background Art
Virtually every internal combustion engine-equipped vehicle on the road today is equipped with a fuel filter, to filter out impurities such as bits of dirt and the like from the fuel.
It has been known to use activated carbon and/or other sorbent materials in a fuel filter to remove paraffins and polynuclear aromatics (PNAs). Examples of these types of fuel filters are given in U.S. Pat. Nos. 5,094,747 and 5,900,153.
The useful life of post-combustion emission control devices, such as catalytic converters, is adversely affected by the presence of sulfur-containing compounds in vehicle exhaust.
Due to concerns about the environment, it is expected that new, stricter standards for liquid fuel refining will soon be implemented, lowering the allowable amount of sulfur-containing compounds permitted to be present in liquid hydrocarbon fuels, such as gasoline, fuel oil, and diesel fuel.
Furthermore, it is well known that very small concentrations of sulfur-related compounds in gasoline may generate “rotten egg” or other objectionable odors in vehicle exhaust. Nearly every driver has been caught behind or near another vehicle which is burning sulfur-containing fuel. It is therefore advantageous to minimize the concentration of sulfur-containing compounds in liquid fuels.
In addition, the development of new technologies, such as fuel cells, will soon require high-purity liquid hydrocarbon fuels for processing. Sulfur-containing compounds, if present in fuel, are likely to adversely affect such new technologies.
Petroleum fuel refiners continue to improve manufacturing processes, to minimize the sulfur content of fuels.
However, notwithstanding the ongoing efforts of industry to minimize sulfur content, many commercially available liquid fuels still include some sulfur compounds therein, such as thiophenes and similar compounds.
Although petroleum refiners continue to work on sulfur removal, little has been done in the area of post-refinery fuel filtration to remove sulfur-containing compounds from fuels at a point of use thereof.
There have been some limited efforts to filter sulfur and other contaminants out of gasoline by the end user, after the gas has been installed in a vehicle. For example, U.S. Pat. No. 4,895,640 to Jackson discloses a method for removing impurities from a petroleum fuel. While this reference mentions sulfur compounds as one type of filterable impurity, it is not focused strictly on sulfur compounds.
As disclosed in U.S. Pat. No. 4,895,640, the method of Jackson includes a step of filtering fuel through a two-part filter arrangement, in which a first filter includes a cellulosic material, a solid organic acid and a chromate compound. In the claimed method of Jackson, the fuel is also passed through a second filter apparatus containing a cellulosic material, the second filter apparatus also containing water. In following the method of Jackson, the filter apparatus is electrically grounded. A similar invention by Jackson is disclosed in U.S. Pat. No. 4,211,639.
The assignee of the present invention has developed a new type of ‘wicking’fiber material that has been used for some filter applications. This material includes hollow spaces within the individual fibers, and this hollow space may be used to house a reactive or adsorbent material. Some issued patents relating to this wicking fiber, and to filters containing this type of fiber include U.S. Pat. Nos. 5,057,368, 5,704,966, 5,713,971, 5,744,236, 5,759,394, 5,891,221, 5,902,384, 5,951,744, 6,004,381, 6,048,614, 6,117,802, and 6,127,036. Other patents using this fiber technology are pending.
A need still exists in the art for a fuel filter for installation at a point of use of fuel, such as on a vehicle, which filter is adapted to reduce the concentration of sulfur-containing compounds in a liquid fuel.